Possibly the biggest boost to the male ego since chest hair, GPS Satnav units have saved us from having to “pull over and ask for directions!!!” Nuh-uh sweetie-pie, I got this with my GPS. Don’t give me directions, just give me an address and I’ll be there! Oh technology, we all love you, keeper of peace in the car – until there’s no signal. This never happens when you’re somewhere nice and safe, it always happens in places like under the bridge in Detroit, Hunt’s Point in New York City, or apparently anywhere in Ireland.

So what can you do? How can you make sure that you’ll get that link up that you need with the eye in the sky? Well, let’s first take a look at what might be causing the sat nav signal problem.

No Line-Of-Sight

The type of signal that satellite communications uses needs to have a clear line of sight between your Satnav and the satellites it is using. To get a proper fix on your location, you’ll need to be in the line of sight of at least 3 GPS satellites. Currently there are 27 in orbit -24 active and 3 spares in case one breaks down or falls out of the sky. It could happen.

As you can see in this animation of the GPS network, the number of satellites possibly visible to any spot on earth changes through the day, from 8 to as many as 12. Of course, when there are only 8 satellites visible, the chances of blocking out 6 or more is somewhat greater. This would explain why sometimes you have a signal and sometimes you don’t, even when you’re in the same spot. If you want to learn a little more about how GPS works, then check out the article, How GPS WorksHow GPS Works [MakeUseOf Explains]How GPS Works [MakeUseOf Explains]As an avid gamer, I’m surprised by the correlation between GPS-like features in modern video games and the proliferation of GPS technology in mundane life. When I was a kid, paper maps and cartography were...Read More.

These satellites also broadcast their signal with only a measly 50 watts of power. To get your head around that, imagine a 50 watt light bulb in orbit over Earth. Yep, it’s that weak. It might not surprise you then, that the issue could be your car windshield, if it has some types of metallic laminate or coating on it. If your GPS worked before in the same car with the same windshield that probably isn’t the case. If you have replaced the windshield, tinted it, or got a different car, this could be the problem. You may need to look into getting an external antenna, if there is one available.

Knowing how weak the signal really is, even the weather can interrupt the signal. It is amazing how bad the weather really has to be to do that, but it can. This in effect is known as Rain Fade. Typically you need an intense thunderstorm, snow blizzard, or ice storm conditions to cause this issue. The storm doesn’t always need to be exactly where you are at either, if the line between the satellite and your Satnav happens to pass through a storm. There isn’t much you can do about it if this is the case. You probably shouldn’t be driving anyway.

If you happen to be in a deep valley, like a fjord or downtown in a city with a lot of skyscrapers, you might not get all the connections that you need. Perhaps you happen to be parked right in the shadow of a building, or even in a parking lot with some sort of roof or awning over it. Even just being set back from the windshield of your car can be enough of an obstruction. General rule of thumb – if there is a shadow on it, you might not get a signal.

Software Issues

Many Satnavs have a GPS Simulator mode. This mode is intended to save power and estimates where you are based on information it already has. When in this mode, the Satnav doesn’t try to acquire a signal, so you need to make sure this mode is disabled.

Sometimes, it just takes a while to acquire a signal. If you’re starting it up in an area where you normally use it, the Satnav already has some information to work with and can acquire a signal in seconds. If the Satnav isn’t aware of your current position or the time, it may take up to 20 minutes to get the signal. You need to remain in the same spot for several minutes while the device tries to get signals. Sometimes, patience really does work. Of course, all things being in working order so far, if it takes more than 5 minutes, you may have another issue.

First, make sure that everything on your GPS device is up to date. Check the manufacturer’s website to see if there are any updates necessary, either for the firmware or the maps. Once you’ve performed the updates, see if your device will pick up a signal.

No signal still? You may want to try what is referred to as a Soft Reset. A Soft Reset puts your device back to almost factory-settings mode, depending on the device. You may only lose your timezone setting, or you could lose all of your customization. It depends on the device and model. The Soft Reset procedures are fairly simple and usually don’t require any tools, except maybe a paperclip.

For some Garmin devices, it’s like forcing a restart of a Windows computer – simple as holding the power button or slide in the on-position for a few seconds. For some other Garmin devices, you remove and re-insert the battery, like you would on a smartphone. For some Tom Tom devices, it requires using a paperclip inserted in the Reset hole somewhere on the device.

Did that work? No? Well you could try doing a Hard Reset, which sets your Satnav back to the factory default savings. Eject your SD or mini-SD card and back up your information, as a Hard Reset will wipe all your settings. For many Garmin devices, you power down the device, then power it up with your finger in the bottom right hand corner. You should get a prompt asking “Erase all user data?“. Press ‘Yes’. The device will reset and power back on.

For many Tom Tom devices, a hard reset can be done through the on-screen menus. Again, make sure you’ve removed any memory cards and backed up all the information you can. This is a factory reset and your information will be lost.

Hardware Issues

If you’ve taken the steps to ensure that it isn’t an issue with something being between you and enough satellites, it is possible that the issue is with the GPS unit. Many of these devices are mounted on dashboards or windshields, and we all should know that heat and electronics aren’t usually friends. Perhaps it’s been a terribly hot day, and the windows are up on the car. The device could reach internal temperatures that could cause the Satnav to not work. The heat may even possibly permanently damage the Satnav.

If you can, take the unit out of the car and put it somewhere at room temperature to let it cool down to normal operating temperatures. (Under 80°C and above -30°C is an estimated operating range, it may vary for your device so check the manufacturer’s specifications.) Then take the unit outside and try it again.

If the GPS unit still won’t acquire a signal, there’s a good chance that the unit has some serious internal issues. The antenna is housed internally on most of these devices, and may have issues. There is also an internal battery, similar in function to the one on the motherboard of your computer. These do die eventually, usually around the 5 year mark – sometimes shorter, sometimes longer. Or it may simply be that the internal electronics were damaged by a power surge, being dropped, or some other hazard. If it got wet, try following the instructions in our How To Save A Wet Cell Phone Or TabletHow To Save A Wet Cell Phone Or TabletHow To Save A Wet Cell Phone Or TabletI’ve got bad news for you. Dropping your phone in a puddle of water, bath, sink, toilet – even getting caught in a heavy shower – will leave it irreparably damaged. The same goes for...Read More article. It pretty much applies to Satnavs as well.

If you suspect any of these things is the issue, you could send your device in for repairs. Or, if you’re terrifically handy with electronics and a soldering iron you might give it a go yourself. In which case, I’m not sure why you’re reading this, you probably know more about these things than I do! However, I think with all things considered, you’ll probably be further ahead if you just replace the unit. Or buy a paper map, when you stop at the gas station to ask for directions.

The Take Away

Whether you are using a dedicated GPS navigation system or just the GPS function of your smartphone, there are a myriad of things that can potentially cause your device to not pick up a satellite signal. Use your logical troubleshooting skills, and the tips above to try to solve the problem. If the problem is still unsolvable, know that there are several low-tech methods to fall back on. Which is best if you have those things in the car already, like a road almanac, and you know how to use them. You can get your unit fixed or maybe even replace it before it you head of on your next grand adventure. Even though hope for your Satnav is lost, not all hope is lost and you don’t have to be either.

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David Lee

May 3, 2017 at 2:39 pm

I have a brand new Binatone U505 Satnav but it will not work inside my car on the windscreen, I take the sat nav and hold it outside the car and suddenly it bursts into life , i replace it on its holder on the screen and it reverts back to "no signal detected" I have a Citroen Picasso 05 model so can anyone tell me whats going on ?

i have bought GPS vk16E. I am receving time information but not the corrdinates. The output i get is. Here value before N and E are alawys 0. Any idea sir.
$GPGGA,002440.030,0000.0000,N,00000.0000,E,0,00,,0.0,M,0.0,M,,0000*42
$GPRMC,002440.030,V,0000.0000,N,00000.0000,E,,,280908,,,N*7C
$GPVTG,,T,,M,,N,,K,N*2C
$GPGGA,002441.030,0000.0000,N,00000.0000,E,0,00,,0.0,M,0.0,M,,0000*43
$GPGSA,A,1,,,,,,,,,,,,,,,*1E
$GPGSV,3,1,12,20,00,000,,10,00,000,,31,00,000,,27,00,000,*7C
$GPGSV,3,2,12,19,00,000,,29,00,000,,04,00,000,,11,00,000,*7C
$GPGSV,3,3,12,16,00,000,,28,00,000,,26,00,000,,15,00,000,*77
$GPRMC,002441.030,V,0000.0000,N,00000.0000,E,,,280908,,,N*7D
$GPVTG,,T,,M,,N,,K,N*2C
$GPGGA,002442.041,0000.0000,N,00000.0000,E,0,00,,0.0,M,0.0,M,,0000*46

I don't have any type of GPS magnet in my brain so I have been using Garmin GPS units for several years. Sometimes, I will print out a map from the computer or from AAA and then compare the directions.

I've got to say that ever since my little brother gave me my first GPS I've been hooked. I used to drive a truck in Southern California ( mostly in the L.A. area) and using the Thompson Guides I managed to get around fairly well. Couple that with the fact that I have a pretty good sense of direction. Since I moved here to New England, the maps were OK at best. But when my brother gave me a GPS, It has saved my bacon on more than one occasion. Especially in Boston where there are so many "one-way" streets or the traffic won't allow you to stop and look at the map. I like the one I have now because it not only tells me when I should arrive at my destination, but also lets me know the traffic conditions.

TomTom in car navigation - That does sometimes have problems getting a location fix but those can be minimised by connecting to a PC to get the updated almanac data and leaving the device turned on even for familiar journeys so when you switch on it "knows" where it was last (this is based on the ephemeris data - a complete satellite lock means ephemeris data had been downloaded to the GPS device, it contains very accurate positioning data for the satellite for the next 30 minutes). Ideally leave the satnav on all the time so it won't lose ephemeris data. Apart from that if you are moving it will take longer to get a fix so turn on as soon as you get into the car and wait for a satellite fix. If you are moving and not got a fix after a few minutes turn off and back on seems to reset the search process and is often sucessful (again best if not moving so I turn off and back on as I'm approaching traffic lights where I will be stopped for a while.)

Panasonic camera with GPS - that too has an almanac download available (They call it "GPS Assist data").

Smartphone - I only turn on the GPS if I need to know my location and don't have any alternative as GPS seems to gobble battery power. One reason smartphones can appear to work better than in-car satnavs in terms of acquiring location is that the GPS function is probably left permanently on while in-car systems are more likely to be powered off when not in use and hence the ephemeris data expires. I tried using my smartphone as a satnav but found the base maps on TomTom were far better, smartphone would try to send me down "bus only" routes for example. Also smartphone relied on a mobile data connection for maps whereas TomTom has the entire UK database on-board.

Dash-cam - came with separate GPS aerial and seems to be quite effective, as it's a far east import (cheap) I didn't have high expectations of the GPS feature it was just a bonus, I'd bought it for the trip-video feature so was favourably surprised by the GPS.

Hikers dedicated GPS (Garmin) - by far the best at capturing signal and maintaining location even in difficult situations like in forest or canyon. I don't know but I wonder if it interpolates and predicts when too few signals are available - i.e. it knows your recent speed and direction so can know where it "expects" you to be and uses that in conjunction with any data it is still getting from 1 or 2 satellites. I made that struggle today in a deep narrow canyon, the resulting mapis scribble but never more than 30-40 metres from where I was - a previous model in the same situation suddenly placed me 1km away.

The downloadable almanac data files some companies provide for their devices have the predicted satellite positions (less detailed than ephemeris data) for the next month(?) so the GPS "knows where in the sky to look".

3 satellites are sufficient to give 2 dimensional location (latitude and longitude), 4 is the minimum if you need altitude as well. Additional satellites improve accuracy largely because there are various possible distortions to the signal from a satellite - for example signals may reflect off tall buildings.
Location accuracy is around 20 metres. Normally that's OK but while 20 metres off in latitude/longitude is probably OK, just a few seconds walk, 20 metres vertical error is the equivalent to climbing a 6 story building.
A friend asked me to investigate a report from his wristwatch GPS. It was reporting that a recent hike had involved a climb of over 1000 metres whereas his perception was that it could only have been 200 metres at most. Analysing the raw data file it became clear most of the reported ascent was when he'd stopped for lunch. He had stopped beside a tall cliff blocking off half the sky so he had fewer satellites available to view. Between consecutive readings, just a few seconds apart, his reported altitude changed by as much as 10 metres (he assured me he'd not fallen off the cliff which would be the only way to obtain such a quick change of altitude!). These errors accumulated to give the eventual false total.

I used to own a Sony sat-nav, with a massive screen for a nice view - I used it twice, and twice only. Two reasons, I didn't have a smart phone at the time and I'm usually quite good with looking at a map, remembering my route and just driving from A to B. Then I got a Nokia with sat-nav-like features (through a combination of J2ME Google Maps and a bluetooth GPS transceiver) which helped while I was doing a part-time delivery job. I since sold my sat-nav and have never looked back. Since that Nokia I've been through an array of smart phones (quite a few on loan basis because I had a very generous boss at my previous job) and I've found that they pick up GPS and AGPS signal miles faster than a traditional sat-nav. Even now using a HTC Radar (Windows Phone) I always have location services enabled, and from loading the Maps app it takes no more than 5 seconds to locate my position 99% of the time.

The times I need my GPS the most are the times it doesn't work. Often I fly somewhere for business - I pick up a rental car at the airport and set my GPS for the address I want - and it takes so long to figure out where it is, I'm either at the customer already or completely lost.

With 20+ years of experience in IT, training, and technical trades, it is my desire to share what I've learned with anyone else willing to learn. I strive to do the best job possible in the best manner possible, and with a little humour. Keep in touch: Twitter - Facebook…